You can easily prepare this ahead of time. Simply make the mixture, divide into cups, and store in the fridge until ready to eat. Dust with cocoa powder right before eating.
Depending on where you live, cream may vary. If you can't find cream that's specifically 35%, don't worry! Any cream with a fat content within the range of 30-35% will give you the desired results (basically just cream you would use to make standard whipped cream).